1. Purpose of the Invention
This invention relates in general to certain new and useful improvements in shielding devices for ignition system components used in hydrocarbon combustion engines, and, more particularly, to shielding devices for use with spark plugs, coil and distributor associated with an engine forming part of the vehicle.
2. Brief Description of the Prior Art
Hydrocarbon combustion engines which employ spark ignition systems and components in the ignition system such as a distributor and coil for generating a spark in a combustion chamber result in the production of radio frequency signals emanating from the ignition system. In addition, the arcing of spark plugs and the other components in an ignition system and the potential for arcing in other portions of an electrical system forming part of an internal combustion engine generate substantial electrical noise. Various shielding devices have been proposed for use about the spark plugs and other components of the ignition system. In military-type vehicles and other apparatus where radio equipment must be operated and in other vehicles and apparatus where radio frequency interference is undesirable, shielding jackets have also been used around ignition wiring harnesses.
While a spark plug may be encased in a permanent shield to obviate these problems, the permanent shielding is quite expensive and, therefore, economically undesirable. This is particularly true since the spark plug is often replaced with the result that the shielding is also replaced.
The prior art is exemplified by my prior U.S. Pat. No. 3,697,796, granted Oct. 10, 1972, for SPARK PLUG SHIELDING. As shown in my prior patent, the spark plug is enclosed in a shield or enclosure which is connected to the plug and provides a wrench section for enabling the plug to be screwed into the block of an engine, the shield also providing a connector means for a shielded spark plug wire.
My copending application Ser. No. 847,124 filed Oct. 31, 1977, also discloses a shielding system for oriented spark plugs. This shielding is used with more sophisticated engines and turbines where it has become the practice to positively orient the spark plugs in the block or head so that the electrodes of the spark plug are positively oriented in the combustion chamber. Orientation of the new type spark plugs is accomplished by the provision of complemented key and keyway means in and on the block and spark plug. In such an assembly, separate means must be employed to clamp the spark plug in place in the socket in the engine. The typical clamping devices, however, interfere with the use of effective radio frequency shielding.
Applicant is aware that relatively expensive shielding devices have been used in connection with spark plugs, coils and distributors of vehicle electrical systems. Applicant knows of no previous system which employs relatively simple shielding devices for the distributor and the coil and which operates in conjunction with a relatively simple spark plug shield for substantially reducing the greatest portion of radio frequency signal emanation from the ignition system of a vehicle.